The definition of a mixed bag, Constantine has the potential to both grasp your attention and lull you to complacency. It's another comic book translation from a not-so-well-known source, and although the material has much promise, the presentation of it doesn't ring any new bells. Its story and look are inherently intriguing, but they don't seem to take it anywhere. Anchored by the central performance of Keanu Reeves -- whose good bit of natural onscreen charisma makes up for his limited acting talent -- the movie coasts when he coasts.

Reeves takes what is originally a British character -- John Constantine -- and turns him into, well, Keanu Reeves. So while the strengths of Reeves himself can do much to carry a film, the character itself isn't given much of a stage. For a comic book character to give up his/her persona to the familiarities of a famous actor will always affect the character's impact; after all, the appeal of any hero with his/her own comic depends on that character's fleshing out. For what it's worth, Reeves turns Constantine into another version of Neo from The Matrix. In this way, Constantine himself doesn't get to stand out, unlike the way, say, Ron Perlman made Hellboy stand out and Wesley Snipes gave Blade his edge.

Bringing up those two characters and their respective movies also places attention on Constantine's look and feel. It's as if the movie followed what has now become a standard "dark comic book" template for tales about dark heroes fighting mysterious forces. It's an amalgam of well-churned ingredients, a mix that includes The Matrix, Hellboy, Blade, Underworld, and perhaps even Men in Black (think bugs and big guns). Constantine uses some bold angles, nice shots, and suspense-building rhythms, but most of it just feels familiar. For better or for worse, its predecessors have conditioned us.

And perhaps all that would have been enough for the film to get by, but it also takes a few too many wrong turns, most noticeably in its overall tone. This is a story about fear-inspiring forces of heaven and hell, and, for the most part, its characters take what's going on very seriously. But then these little moments of comedy insert themselves, and, while the humor is always welcome, their timing tends to throw the mood off. Much of this is intentional, but some of it is not. The very first scene of the movie might just say it all -- in it, something very serious happens, but it's shown in such a way that your inclination, after initial shock, might be to chuckle. The filmmakers may be trying to ask the audience to take the story lightly, but given its subjects of Catholic sin, suicide, visiting hell, and eternal damnation, it might be undercutting its own effectiveness as a suspense machine.

Constantine reminds me of Forrest Gump's box of chocolates. Reach inside and get some fine performances, like from Djimon Hounsou, or cool characters, like Gavin Rossdale's Balthazar. On the next draw, you could get a distinct lack of memorable action scenes and a draggy middle section. Reach in again and find a very cool scene of a character getting sucked away through a building; and then next time you'll get a silly finale, which features a good performance for an unoriginal version of a well-known character, and an unlikely and thankless turn for another character played by an underappreciated actor. And while the box of chocolates may be full of surprises bad and good, in the end, it's only another box of chocolates.

(Released by Warner Bros. Pictures and rated 'R" for violence and demonic images.)